July 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
The effectiveness of corn meal and soybean oil meal as carriers was due evidently to the presence of antioxidants which supplemented those in the concentrates. Soybean oil meal was more effective in preventing autoxidation than corn meal. The greater rapidity in the loss of vitamin A or @-carotenewhen the products were mixed with glucose than when stored alone may be due either t o greater dispersion of the products or to the presence of oxidants in the glucose. The two products that were the most stable alone (Nos. 1 and 2) were also the most stable when mixed with glucose. They retained more than 60% of their initial vitamin A content after 6 months of storage when mixed with glucose as compared with 37% and less for the other products. SUMMARY
Seven different dry commercial vitamin A products containing 150 to 1500 micrograms of vitamin A or carotene per gram retained 60 to 85% of their initial vitaniin during a 6-month storage period in the dark a t room temperature. The highest stability
1593
was shown by products which employed vegetable meals or the antioxidants which they contain. A portion of each of the products was mixed with corn meal, soybean oil meal, or glucose in such proportions that the mixtures contained approximately 10 micrograms per gram of vitamin A or its equivalent in esters or @-carotene. Soybean oil meal (expeller) improved the stability of the vitamin in most of the products. Ground yellow corn showed a similar effect but t o a lesser degree. Glucose (cerelose) diminished the stability in all cases. LITERATURE CITED
(1) Buxton, L. O., IND.ENG.CHEM.,39, 225 (1947). (2) Dassow, J. A,, and Stansby, Maurice E., J . Am. Oil Chemzsls’ SOC.,26, 475 (1949). ( 3 ) J . Assoc. O f i c . A g r . Chemists,31, 111 (1948). (4)Maynard, L. A,, “Animal Nutrition,” revised ed., p. 187, Piew York, McGraw-Hill Publishing Co., 1947. (5) Mitchell, H. L., Schrenk, W. G., and King, H. H., IND. ENG. CHBM.,41, 670 (1949). (6) Schaefer, H. C., J. Assoc. Ofic.Agr. Chemists, 33, 615 (1950). R E C E I V October ~D 4,1960. Paper No. 478 of the Purdue Agricultural Experim e n t Station.
Protein Evaluations of Yeast Grown on Wood Hvdrolvzate J
J
ELWIN E. HARRIS, GEORGE J. HAJNY, AND NIARTHA C. JOHNSON Forest Products Laboratory, Madison, Wis.
This project was undertaken to determine the conditions of maximum growth of six strains of fast-growing yeast, using wood hydrolyzate as a source of sugar, and the comparative value of yeasts as a source of protein for animals. All six strains of yeast grew rapidly on the wood hydrolyzate in a continuous propagator, using 90 to 96% of the reducing matter in solution, giving yields of 42 to 58% of yeast with 4S to 51% protein. These six strains of yeast, plus a sample of yeast grown on sulfite waste liquor, were fed in comparison with casein as a source of protein to protein-depleted adult rats. Regain in weight with the eight strains of yeast was less than with casein, but when supplemented with methionine, weight regain with yeast was equal to casein. Wood hydrolyzate may be used as a source of sugar for the production of high yields of yeast that is high in protein. This low-cost yeast, when supplemented with small amounts of methionine, provides a source of protein comparable with animal proteins, thereby bringing about a rapid, low-cost, ef6cient method of converting waste nonedible carbohydrates into an edible complete protein.
S
IX strains of yeast previously shown (9)to be readily acclimatized for growth on wood hydrolyzate in batch propagations in shake flasks were grown continuously in a Waldhof-type yeast propagator. Samples of these six yeasts were fed as a source of protein t o rats to determine availability and value as a source of protein. Experimental production of a Torula yeast on wood hydrolyzate (6, 6, 8) has shown that 8 yeast propagator provided with a means for continuous addition of sugar solution and continuous removal of spent solution and yeast, and with a means of controlling foam, has the, best results. A small experimental propa-
gator having these features was constructed (12) and used for preliminary work.
It was determined in this equipment that 5 to 5.5 grams of reducing sugar, as a 5% solution, could be fed continuously per hour per liter of propagator operating capacity. Yeast in a propagator having an operating capacity of 34 liters gave good groFth when fed 3.4 liters per hour of a 5% solution of wood sugar with the necessary nutrients. Later a modification of the first propagator with an operating capacity of 150 liters was built. This employed a squirrel-cage type of ropeller for distributing the air As in the liquid and pumping the %guid t o control foamin much as 20 liters of 5% sugar solution per hour could be fe%fully acclimatized Torula east in this propagator with practically complete utilization of (0th hexose and pentose sugars. Nutrient requirements (6) were found t o be 3.4 pounds of nitrogen as ammonia, ammonium sulfate, or urea, 0.71 pound of phosphorus as sodium phosphate salts, and 0.58 pound of potassium as either potassium chloride or sulfate for each 100 pounds of reducing sugar in the feed. The air requirement was 80 cubic feet for each pound of sugar in the feed, or 2.3 cubic feet per minute when the rate of feed was 16 liters of 5% sugar per hour. Under equilibrium operating conditions the liquid was changed to a free-flowing foam three times the volume of the liquid so the actual li uid in the 150-liter propagator was 50 liters. d e n a feed rate 16 liters an hour was used, the throughput time was 3.12 hours. At a feed rate of 20 liters, the throughput time waa 2.5 hours. Utilization of reducin material was slightly higher when the throughput time was axout 3 hours than it waa with a 2.5-hour period.
3
EQUIPMENT
The yeast propagator was a water-jacketed stainless-steel tank with a total capacity of 150 liters. Inside was a draft tube of about one third the diameter of the tank and a rotating air sparger mounted with a top and bottom bearing similar to the small laboratory model previously described ( l a ) . Sugar solution containing the nutrients was fed in by a proportioning pump. The level of the contents of the propagator was controlled by an electronically operated valve in the bottom. Yeast and spent liquor were pumped from the bottom of the propagator to a defoaming tank, from which it was pumped to a continuous yeast
1594
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 43, No. 7
Candida krusoides. B strain of yeast obtained by American observers in Germany after Feed Rate, .\ir Kate. ___ Condition- in ProPapator" Total the war ( 1 4 ) and designated Litersf Cu. Ft.1 Reducing Yeast Dry Sugar Yeast ae Candida arborea, but later Time Hour Xin. PH sugar, % vol., R yeast, YG Used, % Yield, %, classified as Candida krusoides, Torula uftlis S o . 3h had been shown in previous 4 1. o :,2 0 89 3.0 0 6 .. Start 6 1.0 4.8 0.78 1.5 .. .. .. After 4 hours tests (9) to be suitable for After 8 hours 8 1, 3 4.8 3.32 9.0 After 24 hours 12 2 0 4 8 028 10.0 2:is 96:4 4i:z growth on wood sugar. This After 48 hours 16 2 3 4.4 0.27 10.0 2.11 94.6 45.5 yeast started more slowly than After 72 houre 16 2 .-I 4.7 0.28 10.0 2.10 94.3 45.4 16 2 3 After 96 hours 4.7 0.19 10 0 2.19 96.4 46.2 Torztlautilis S o . 3, but after 48 18 3 0 4.8 0.22 10.0 2.17 95.6 46.1 .After 5 days 18 3.0 4.7 0 24 10.0 2.19 95.2 46.7 After 8 days hours it was growing rapidly 18 3 .o After 12 days 4.7 023 10.0 2.18 95.4 46.3 with good yields and good Candida kruso7dirr sugar utilization. Table I S t a r t" 0 1 0 5,2 0 3 shows the conditions for pro4 0 78 1 0 5.2 2 0 8415 After 4 hours 4 1 0 0 55 89.0 4.2 After 8 hours duction and yield of C a n d i d a 8 2 0 n.2 0 33 34:6 93.5 After 24 hours 1'64 12 2 0 3 .2 94.5 44.0 0 28 After 48 hours 9 0 2 11 krusoides. This yeast appeared 16 2 3 3 2 0 24 10 0 '2.19 95.1 45.0 After :3 days to use a greater amount of the 16 2 5 3 2 0 23 10 0 95.0 45.0 After 4 days 2.17 0 25 95.0 45.0 16 2 ;i 0 2 10 0 2 18 After 5 days organic acids in the solution 45.0 18 0 22 12 0 95.0 After 7 days 3 0 p,2 94.5 18 3 0 0 22 12 0 44 0 and the p H of the solution went a.0 After 8 days higher than others did. 0 1.5 4 0 Mycotorula ZipoZytica. A Start 1 1.3 a 1 0 36 10 0 93:3 After 3 hours strain of yeast from the Unili 0 41 11.0 2 50 92 3 2 3 5.1 After 8 hours 12 2 3 0 37 AEtPr 24 hours 5.1 10.0 93 1 vereity of \T7isconsin collection, 0 38 12 2 5 4 9 2 ' 31 11.0 92 9 After 2 days 2 3 11.0 92.9 14 0 38 designated as P13 in a previous After 3 days 4 8 11.0 92 9 14 2 .J 0 38 2 . k After 4 days 4 s publication on production of 11 2 2 55 16 2.7 0 71 94.8 51.0 1.9 After 5 days yeast on wuod sugar ( I O ) , was The propagator was held at n toiiipeiatuie of 30' C grown on wood hydrolyzate b The feed had a sugar conrenr of 4 94% and a pH of 3 98 The feed had a s n q m content of 5.06% and a p H of 3 92 containing 6.34Y0 reducing d T h e feed had a sugar Content of i 347, and a pH of 3.9 sugar. This yeast grew rapidly, and in 8 hours it,had devcloped the ability to use rvood hydrolyseparator that delivered yeast, as a cream with about 90% cell zate rapidly and producied good yields of yeast. Table I gives The yeast cream was heated t o rupvolume, or 2270 dry solids. the condit'ions for gron-th and thP yield of .V~~/cofor~clo Zipoture the cells and then dried on an atniospheric double-drum dryer lytica on wood hydrolyzate. with 26 to 36 pounds of *team pressure per square inch on the Toiula utilis thernzophilis. This yeast is characterized by its rolls. ability t,o xithstand higher temperatures. I t n-as grown a t 37" C. YE.AST PRODUCTION rather than at' 30" C. This difference in temperature made an The inoculum used for the production of yeast was prepared as apprwiable difference in the amount of cooling m-ater required to previously described (6, 7 ) . Sugar was determined by the maintain tempcrature. Yeast growth was rapid, and good yields method of Schaffer and Soniogyi (13, 16). Yeast cell volume was i\-ere obtained after 12 hours of continuous production. The determined by placing 10 ml. of the yeast suspension in a centricondit,ionsfor growth and yield of products are shown in Table 11. fuge tube, spinning a t 2000 revolutions per minut,e (r.p.m.) for Candida albicans. In previous experiments (9)Candidu alhi10 minutes, and reading the volunie of yeast. Xitrogen content rans had shown ability to maintain activity when left in cold of the yeast was determined by the Kjeldahl method. storage with v-ood hydrolyzate as a growth medium, bctter than The ]-east production was &rted by placing about 12 liters of some other strains. (One of t,hc rcviervcrs of this manuscript reyeast inoculum produced by aeration in a 20-liter bottle in the ports he has found Cclnlidu alhicans to he a pathogen. 40trouble propagator and then starting the aerator and the pump for the was found n-ith the organism used in this Fr-ork, but further work sugar solution. A thermostat controlled the flow of Tvater should not, I)e undertaken until t,l.iia propert>- is known.) This through the water jacket of the propagator to hold the temperayeast viae grown on wood hydrolyzate h cont,inuouspi opagation. ture a t 30" C. or other desired temperatures. At the beginning, It did not grow 80 fast nor use the sugar so rapidly as some other solut,ion cont,aining approximately 5% sugar produced hy t,he strains of yeast. The conditions Cor growth and yiolds are hydrolysis of aspen ~ v o o dwith O.?iY0sulfuric acid a t temperatures given in Table 11. ranging from 150" to 180" C. (3)was int,roduced a t the rate of 4 Sacchn,ontyces ceiwisiae S o . 46. This strain of >,east was liters per hour until the quantity of yeast was built up to equilibfound to give good yields of alcohol from wood hydrolyaatcs ( 4 ) rium conditions and was t,hen,increased gradually until further and to maintain high activity after many transfers. I t did not increase resulted in a 1on.er sugar utilization. A period of about grow so rapidly nor give so high yields as some other strains of 12 to 96 hours of continuous operation rvas required to reach the yeast: hut, after 3 days it utilized 95 to 9670 of t,he reducing suhmaximum feed rate and maximum sugar utilization. stances in solution. Thc conditions for growth arid yield arc Torula utilis No. 3. The propagator TT-BS started with 12 litcrs given in Tahle 11. of inoculum produced I)>- aeration of a pure culture of Torula Table I11 coinparc's thc rates of sugar utilization, thc extent of utilis KO.3 in a 10-liter bottle. The inoculum contained a 374 sugar utilized, yeast cell volume produced, the yeast yield, and cell volume of yeast. A solution of wood sugar was fed in at, a the protein content of the six strains of yeast. The Utilization of rate of 4 liters per hour and r a s gradually increased to 18 liters total volatile organic acids wis determined a t frequcJnt intc,r.vtils per hour. The air rate vias increased as the sugar in the feed and was found to hc 6.5 t o 70700. increased. The conditions for production and yield of Toiuln utilis KO. 3 are shown in Table I. Deterniination of reducing YEAST AS A SOURCE OF PROTEIN F 0 0 1 ) sugar before and after yeast growth showed utilization t o be 95 to Studies were made on the protein availabilitv in yeast groivii 011 96%. It was actually better than that, because nonsugar reducwood hydrolyzate, and this availahility was compared ivitli t h a t ing substances accounted for some of the material not used. ,
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July 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
1595
protein, yeast or casein equivalent to 0.2 gram of nitrogen was added to the nonprotein - Conditions in Propagator __ 'Iotal Feed Rate, Air R a t e , diet of the rats for 5 days, after Sugar Yeast Cu. ,Ft./ Reducing Yeast Dry Liters/ Time Hour 1Min. pH sugar, % vol., % yeast, % Used, % Yield, % which gains in weight were measured. The average gain Torula utilis thermophzlis" per day is shown in Table IV, 0 1.5 4.8 .. Start 4 1.b 0:31 9'5 4.8 rlfter 6 hours run 1. In this series a l l the 4.1 0.40 11 . 0 2'65 92:o 5s: 0 2.0 12 After 8 hours 0.36 11.0 .. 12 4.0 .. .. 2.0 .4fter 24 hours of yeast grown on wood strains 0.32 11.0 2.0 4.0 .. .. .. 12 After 2 days sugar were shown to give 50 to 0.30 11.0 .. 4.1 2.5 , . .. 14 After 3 days 0.26 11.0 16 4.1 .. .. 2.5 After 4 days 85% of the gains made on 0.26 11.0 16 4.1 2.5 After 5 days 16 2.5 0.26 11 0 %:6O 50: 0 4.1 94:s After 7 days brewer's yeast and on casein. Following t,his, the same rats C a n d i d a alhicansb were prepared for a second trial 0 1.0 4.8 .. .. Start 4 4.8 7:0 .. 1.0 , . .. Aftel 3 hours by feeding a standard base rat 5.1 10.5 6 1.7 After 8 hours 0:4s 10 10.0 2:i7 4.5 1.7 96:s 46:O After 24 hours feed for 2 days, and then the 0.47 10.5 12 2.0 2.3 4.6 90.9 49.0 After 2 days 11.0 0.41 nonprotein depletion diet for 12 4.7 2.5 92.0 53.0 2.0 After 3 days 11.0 0.46 91 .o 2.0 4.8 .. 12 After 4 days 7 days. The rats were then 11.0 0.46 2.0 4.8 , . 91.0 .. 12 After 5 days 0.35 11.0 12 2.5 4.8 .. .. 93.2 After 8 days fed the same as in run 1 for 5 days, and the gains in weight Saccharomyces ce7evisias No. 46C 1 5 were recorded. The average 0 .. .. .. Start 4:3 0:44 6 1.7 7:0 After 4 hours gain in weight per rat per day e 1.7 4.5 0.40 9.0 .. .. After 8 hours . . 0.37 8.0 4.7 8 2.0 .. .. .. After 24 hours is shown in Table IV as run 2. 0.16 4.2 2.0 , . 8 8.0 .. After 2 days .. 12 2.0 6.3 0.16 8.0 These agree with run 1 . .. .. . . After 3 day8 4.6 0.22 9.0 2.5 14 .. d f t e r 4 days .. .. As it \vas apparent that some 4.0 0.30 8.5 14 2.5 After 5 days 0.18 14 3.9 9.0 2:ii 2.5 96: 0 42:3 After 7 days growth factor was lacking in 4 0 14 0.20 8.5 2.5 2.08 96.0 After 10 days 41.6 the diet, on the basis of the a The feed had a sugar content of 4.98% and a p H of 3 9. The propagator was held a t 3 i 0 C. tests iiiede with weanling rats, b The feed had a sugar content of ,5,17% and a pH of 3.6. T h e propagator was held a t 30° C. c T h e feed had a sugar content of 5.0% and a P H of 3.9. The propagator was held a t 30' C. it was decided to mpplement the yeast with methionine. OF SIX STRAINS O F YEASTGROWNON WOODHYDROLYZATE Rose ( 1 1 ) has shown that the optimum TABLE 111. COMPARISON Yeast ainount of methionine in the diet vas Maximum Sugar Nitrogen Cell Dry Protein 0.6% of the diet. The rats were eating Feed, Utilized, Utilized, vol., yield, content, Strain of Yeast Lh./Day % % m1./100 Ib./day % 15grams of ration a day. Methionine 95.0 47.0 99 10 19.6 T o r u l a u t i l i s No. 3 50.7 was added to the diets at the rate of 0 09 96 48.3 12 9 5 . 0 C a n d z d a krusoides 21.7 45.4 99 11 45.2 94.0 20.7 MMycotorula lipolytica 46.1 gram per rat pcr day. X o correction 99 11 9 4 . 8 42.3 1 9 . 0 47.6 T o r u l a utilis thermophilis 99 11 33.0 93.0 16.1 47.2 C a n d i d a albicans a a s madc for methionine in the yeast. 96.0 99 37.1 9 15.4 50.7 Saccharomyces cerevisiae No. 46 -4n excess of methionine was shoun in later tests, however, not to produce an increase in growth. in yeast grown on sugar in sulfite waste liquor, yeast produced as a The same rats were prepared for the third test by feeding a standard diet for 2 days and the nonprotein depletion diet for 7 by-product in the brewing industry, and with casein as a control. The first tests were made with weanling rats, by comparing days Then the yeast supplemented u ith 0 09 gram of methioT o r u l a u t i l i s with casein as a total source of protein. The gain in nine was fed for 5 days. The avwage gains in weight per rat per weight of the rats fed 7'oruZa utilis averaged only 60% of that for day are shown in run 4. These tests indicate that yeast supplecasein. Fur became thin on the backs of male rats fed the yeast. mented with methionine is the equivalent of casein for repletion Female rats showed this property to a lesser extent. The loss of of protein-depleted rats. hair was taken to indicate the lack of some essential amino acid. Further tests of the protein values were made by c30mpariiig Yeast was, therefore, supplemented with various amiho acids in soybean meal and casein with Torula utllzs No. 3 and two strain. further feeding tests. The only amino acid that produced imof Fusarium grown on wood hydrolyzate. Run 3, Table IT', provement in weight gain and hair restoration was methionine. shows the repletion values in avrrage gain in grams per rat per When the daily requirement of methionine was added to yeast, gains made by weanling rats were similar to those fed casein. In further tests on the evaluation of yeast as a source of protein, ASSAYO F h O T E I S O r lrARIOCS FOOD YEASTS -4ND TABLE I\r. the method of Frost and Sandy ( 1 , 2 ) was used. In these tests 60 FCSARI[-M AS COMPARED TO CASEIN BY RATREPLETION METHOD adult rats weighing 160 to 190 grams were fed a nonprotein diet, R u n KO.1 2 3 4a 5CL as desciibed by Frost and Sandy ( b ) ,for protein depletion for 12 Source of Protein G a i n / R a t / D a y . Grams days. In that time the rats lost 40 to 50 grams in weight. Then 3.1 2.7 6.2 5.2 3.1 Toiula utzlis No. 3 1.5 grams of casein as a source of protein were added to the diet of ... ... 3.5 5.8 3.1 Sulfite yeast 2 . 8 . . . .,. 5 . 9 3 . 2 Candzda krusoides each rat for 3 days, followed by the nonprotein diet for 4 more ... 6.2 , . . 3.0 3.1 Torula utilzs thermopirilis days. The rats were divided into groups and fed the various 3. 3 6.6 4.2 ... C a n d i d a albicans 3.7 .,. 6.1 ,.. 3.6 Saccharomyces cerevisiae yeasts as a source of protein. 3.4 ... 6.6 .. 3.7 Mycotorula lipolytica 5.3 ... 6.5 ... 5.2 Two other samples of yeast were fed in addition to the six Brewer's yeast 5,3 ... 5.6 5.0 5,5 Casein strains of yeast described above: a sulfite yeast containing 49.2% ... ... ... 4.9 6.4 Casein . 7.3 ... 4.4 . . Soybean meal protein; and a sample of commercial brewer's yeast containing 6 .5 . . . 3.4 . . . ,140 F u s a r z u m Zini, Bolley S-0. i5.3 2.9 ... 40.0% protein. These were compared with casein containing F u s a r i u m lini, Bolley With methionine. 81.6% protein as the source of protein. In each case, assuining that all the nitrogen in the samples was OF Torula u t i l i s thermophilis, Candida albicans, A N D TABLE11. PRODUCTION Saccharomyces ceTevisine KO. 46 ON ASPEN \ I T 0 o ~HYDROLYZATE
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I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 43, No. 7
LITERATURE CITED
day without methionine, and run 5 shows the values when supplemented with methionine. These tests indicate that food-yeast protein and protein in Fusarium is deficient in methionine but when supplemented with methionine give weight gains equivalent to casein.
Frost, D. V., and Sandy, H. R., Federation Proc., 8, 383 (1949). Frost, D. V., and Sandy, H. R., J . Nutrition, 39, 427 (1949). Harris, E. E., and Beglinger, E., IND.ENG. CHEM.,38, 890
CONCLUSIONS
Harris, E. E., Hannan, M. L., and Marquardt, R. R., Ibid., 40,
(1046). ~-_,. -.
Harris, E. E., Hajny, G. J., Hannan, M. L., and Rogers, 9. C., Ibid., 38, 896 (1946).
Six strains of food yeast have been grown continuously and rapidly in high yield and high protein content on wood hydrolyzate with almost complete utilization of sugar and volatile acids. The six yeasts, a sample of sulfite liquor food yeast, Fusarium grown on wood sugar, and casein were fed rotein-depleted adult rats to determine their repletion value. &he food yeasts were found t o have 50 t o 85% of the value of casein. Food yeast and Fusarium supplemented with methionine gave repletion values equivalent to casein and indicate a high value as a protein food. ACKNOWLEDGMENT
The authors acknowledge the assistance given them by H. T . Scott and Carl H. Krieger in planning the protein evaluations, in providing the space for the tests a t the Wisconsin Alumni Research Foundation laboratory, and in evaluating the information obtained. The authors wish t o thank A. J. Wiley of the Sulfite Pulp Manufacturers’ Research League, Inc., Appleton, Wis., for the sample of sulfite yeast, and D. K. Richardson of the Schlitz Brewing Co., Milwaukee, Wis., for the brewer’s yeast used in these testa. This experimental work was conducted with funds provided by the Research and Marketing Act.
2068 (1948).
Harris, E. E., Hannan, M. L., and Marquardt, R. R., Paper Trade J., 125, 34 (1947). Harris, E. E., Hannan, M. L., Marquardt, R. R., and Bubl, J. L., IND.EX+. CHEM.,40, 1216 (1948). Harris, E. E., Saeman, J. F., Marquardt, R. R., Hannan, M.L., and Rogers, S. C., Ibid., 40,1220 (1948). Johnson, M. C., and Harris, E. E., J . Am. Chem. SOC.,70, 2961 (1948).
Peterson, W. H., Snell, J. F., and Frazier, W. C., IND. ENQ. CHEM.,37, 30 (1946).
Rose, W. C., Science, 86, 298 (1937). Saeman, J. F., Anal. Chem., 19,913 (1947). Saeman, J. F., Harris, E. E., and Kline, A. A,, IND.ENQ.CHEM., ASAL. ED.,17, 95 (1945). Saeman, J. F., Locke, E. G., and Dickerman, G. K., U. S. Dept. Commerce, F I A T Rept., 499 (Nov. 14, 1945). Sohaffer, R. A., and Somogyi, N., J. Biol. Chem., 100, 695 (1933). RECEIVED September 5, 1950. Presented before the Division of Agrioultural a n d Food Chemistry at the 118th Meeting of t h e AMERICANCHEMICAL SOCIETY, Chicago, Ill.
Catalytic Esterification of Olefins with Organic R. D. MORIN AND A. E. BEARSE BatteZle Memorial I n s t i t u t e , Columbws, Ohio T h e direct esterification of olefins with organic acids offers an attractive means of preparing many types of esters. I n order to obtain an efficient and practical process, a more active and effective catalyst was required than has previously been used, and the objective of this work was to find such a catalyst. Experimental results have shown that a mixed catalyst comprising boron fluoride and hydrogen fluoride is particularly effective in promoting the esterification of olefins with organic acids. Isopropyl acetate has been prepared from propylene and acetic acid in SOYO yield using this catalyst, and a number of other esters have also been pre-
pared in good yield from various olefins and organic acids by this method. Comparison of the boron fluoridehydrogen fluoride catalyst with other acid catalysts has shown i t to be superior for the catalytic esterification of olefins. Catalyst recovery and reactor corrosion were also studied. Etherification of olefins is also promoted by boron fluoride and hydrogen fluoride. Discovery of a novel and efficient catalyst, boron fluoride-hydrogen fluoride, for the direct esterification of olefins with *organicacids makes this process attractive for the preparation of esters from by-product refinery olefins.
T
one of the raw materials. I n those cases where the alcohol ia derived from a n olefin by hydration, a processing step is eliminated. For example, in the preparation of isopropyl acetate from propylene by the usual method (7), isopropyl alcohol is obtained by the hydration of propylene with sulfuric acid and the ester is then formed by reaction of isopropyl alcohol with acetic acid in the presence of sulfuric acid.
HE production of esters by the catalytic esterification of olefins with organic acids offers a possibility of converting
by-product refinery olefins to more useful and valuable products. The esters t h a t can be prepared by this method have well established uses as solvents, plasticizers, and chemical intermediates. ilt the present time, nearly all commercially produced esters are obtained by the conventional esterification reaction of an alcohol with a n organic acid or anhydride in the presence of a mineral acid catalyst. This reaction is sometimes quite slow, and since it is reversible, some means of driving i t to completion usually must be employed. I n the majority of processes, this involves removal of water as it is formed. The direct esterification of olefins t o form organic esters offers many advantages over conventional esterification methods. I n the f i s t place, a cheap olefin replaces a more expensive alcohol as
CHaCH=CHs (CHa)GHOH
+ HzO -+ (CHa)&HOH &SO4
+ C H I C O OHzS04 H N CHaCOOCH(CHa)z + HzO
I n the direct catalytic olefb esterification process, the ester is obtained directly from propylene in one step. CHaCH=CH,
+ CHBCOOH + catalyst
CHaCOOCH(CH3)z
